Method of forming abrasive surfaces upon high-speed grinding wheels



Jah. 6, 1942.

F. F. GILMORE ETAL METHOD OF FORMING ABRASIVE SURFACES UPON HIGH-SPEED GRINDING WHEELS Filed lug. 2, 1940 \IIIIIIIIIIIIIIH l IIIIIIIIIIV' iiiiiii v 7/ 7 INENTPR BY Km A KW TTO R N EY5 Patented Jan. 6 1942 METHOD OF FORMING ABRASIVE SURFACES UPON HIGH-SPEED GRINDING WHEELS Folliard F. Gilmore, Welleslcy Hills, and Frank W. Kotler, Watertown, Mass; saidKotler assignor to said Gilmore Application August 2, 1940, Serial Nil-349,622

4 Claims.

This invention relates to a method of making high-speed grinding wheels and to the grinding wheels prepared in accordance with such method.

This application is a continuation in part, of our co-pending application, Ser. No. 250,525, filed January 12, 1939, for Abrasive surfaces.

In grinding and polishing operations, for emcient and high-speed production purposes, it is often desirable that the abrasive-containing surface should be moved at a high speed in relation to the work, speeds of between 5,500 and 6,000 superficial feet per minute being considered best practice. within a hardened matrix which is applied upon an annular surface of a rotatable wheel, tube,

metal surface of the'wheel is especially pronounced in the case of the matrices which contain diamond particles. The problem involved in supporting diamond particles in proper position for use in a high-speed grinding Wheel is set forth .in our application, Ser. No. 212,306, filed by us June 7, 1938, wherein is disclosed a suitable matrix and a method of making same, whereby diamond particles may be supported, and a supporting matrix may be built up.

The present invention is directed more particularly to the method, and the means, whereby the matrix may be securely bonded to the underlying metallic surface on which it rests. While we shall refer herein to a matrix which contains diamond particles, we believe that the method and means herein described are useful for bonding any abrasive-containing matrix to its supporting metal surface.

. Referring to the annexed drawing forming a part of this specification:

Fig. 1 shows in cross section aso-called cup- ;shaped grinding wheel of conventional design, :and illustrates the type of structur to whose manufacture our invention is adapted.

Fig. 2 shows, in section and perspective, the

shape of a portion of the annular periphery of this wheel, at the start of operations.

The abrasive is ordinarily held m away at the conclusion of the formation of the matrix.

Fig.'l0 is a view similar to Fig. 8, showing the matrix fully formed on the periphery of the wheel, ready for use.

Referring to the annexed drawing, wherein like reference characters designate like parts in the various figures I An abrasive ,wheel may be of several forms. In the form herein shown for purposes of illustration, it comprises a disc portion II and. an

annular rim l2 projecting laterally of the plane of the disc. Upon a surface- I3 of the annular rim I2 is positioned a hardened abrasive-containing matrix M. For illustrating the present invention it will be assumed that the material of at least a portion of this matrix is applied to surface l3 in liquid form and is heat-hardened in place, and that successive layers are built up in this manner to provide the desired depth.

While surface l3 may be formed of any one of a number of available materials, it is often desirable that the entire wheel should be formed of a light strong metal such as aluminum. Aluminum is particularly effective, not only because it is light, but because it may be easily turned and polished. A smooth aluminum surface, however, does not in itself form a satisfactory bond with an abrasive-containing matrix heathardened upon it. The same is true of copper and other ductile materials of the types which 5 annular rim l2 somewhat wider than will ultimately. be required, and cut away sufficient material to form a broad, shallow channel I 5 therein having a smooth or nearly smooth floor l6, and side walls ll, l8 whose height above the floor is the same as or slightly greater than the desired depth of the abrasive-containing matrix to be formed in the channel. The width of channel l5 equals the desired width of the annular band of abrasive-containing matrix M. The channel I5 may be formed bymachining, i. e., by cutting away waste metal by the use o'fa tool in a turning lathe, or in any other similar manner.

We then place the wheel in a lathe and turnv it slowly under a cutting tool IS in a suitable holder 20. Tool [9 i of tungsten carbide, chilled steel, or other hard material and is provided with a sharp point or sharpened edge. Tool I9 is applied with a reverse or negative rake, and in such manner as to plow a shallow groove 2| in the smooth floor l6 of the channel I5. During the turning of the wheel, tool I9 is moved gradually from one side of the channel l5 towards the other, thereby forming a spiral'or helical groove. The depth of the groove maybe suited to individual requirements. It may be a few-thousandths of an inch in depth, or it may be somewhat deeper than the groove usually employed on phonograph records. If desiredythe groove need not be helical or continuous but can be cut in the form of a series of concentric circles, the differences in diameter being such as to space the grooves at desired distances apart. We prefer a helical groove, with adjacent courses spaced about .015 inch apart on centers, the groove being slightly deeper than the groove in the usual com- A mercial phonograph record.

In plowing groove 2|, the tool I9 is arranged to remove little or no metal but to cause the formation of a lip 22 at each side of the groove,

and the reverse or negative rake of the tool Where successive courses of a continuous helical groove are closely spaced, the common lip or ridge between adjacent courses of the groove carries along its crest a continuous row of these jagged projecting tongues of metal. If the courses are further removed apart, as suggested in Fig. '7, the lip at either side of the groove will have a projecting series of tongues of metal.

After the floor I6 of channel l5 has been prepared in the manner stated, abrasive-containing matrix may then be formed between the side walls l1, [8 of the channel in any suitable manner. For this purpose we prefer to employ the method of forming an abrasive matrix which is shown in our co-pending application, Ser. No. 212,306, building up successive layers of abrasivecontaining glass fabric impregnated with a heathardening varnish. The first layer may be a primer which is applied in liquid form upon the grooved surface and heated to render it tacky.

This layer forms an intimate and effective bond with the projecting tongues of metal and forms the base upon which successive layers of fabric and impregnating diamond dust and varnish with suspended diamond particles,are laid and heathardened. Each layer is applied separately, and baked in place before the next layer is applied. This procedure is followed layer by layer until abrasive-containing material ll of suitable depth has been built up as indictaed in Fig. 8.

When the matrix has been entirely formed and l the final baking has been completed, the side walls ll, ii! are then machined away, the parts removed being indicated by dotted lines in Fig. 9.

The result is to produce the finished structure indicated in Fig. 10 and Fig. 1.

It appears that the varnish or other heathardenable material which is applied in liquid These jagged projections of the metal,

form upon the floor l6, prepared as herein described, fills th groove 21 and the tongues 23 become embedded therein. When the initial layer or layers of varnish material have been baked in place, the result is to produce a very effective and secure bond between the metallic surface and the abrasive matrix which is formed thereon. We have found that abrasive wheels made in this manner have a pronouncedly long life, may be used at higher speeds. and will not flake or chip in use.

The angle at which the tool 19 is applied must be determined by trial, depending upon the nature and physical property of the metal being grooved. The projecting tongues of the metal appear to be formed only when the tool is given a reverse or negative rake. The phenomenon has its chief usefulness in connection with the ductile metals such as aluminum and copper.

We claim:

1. In the method of preparing an annular ductile metallic surface of a high-speed grinding wheel to receive and retain a layer of abrasivecontaining matrix thereafter to be applied to said surface, the step of machining said surface with a hardened tool applied with a reverse rake in relation to its direction of travel upon said surface and at such an angle thereto as to form a series of minute tongues of metal integral with the metal of said surface and projecting upwardly above the general level of said surface.

2. In the method of preparing an annular ductile metallic surface of a high-speed grinding wheel so as to adapt the same to retain a layer of abrasive-containing matrix thereafter to be applied to said surfacathe step of plowing in said surface a shallow grooveby means of a sharpened tool applied with a reverse rake in relation to its direction of travel upon said surface and at such an angle thereto as to form a series of minute upwardly-projecting tongues of metal integral with the metal of said surface along a lip of said groove.

-3. In the method of preparing an annular ductile metallic surface of a high-speed grinding wheel so as to-adapt the same to retain. a layer of abrasive-containing matrix thereafter to be appliedto said surface, the step of plowing in said surface a series of closely-spaced shallow circular grooves bymeans of a sharpened tool applied with a reverse rake in relation to its direction of 'tr'a'vel'upon said surface and at such an angle thereto as to form a series of minute upwardly-projectingtongues of metal integral with x the metal of said surfa'cealong the lip-between adjacent courses of said groove.

'4. In the method of preparing an annular duc- -tile metallic surface of a high-speed grinding wheel so as to adapt the same toretain a layer of abrasive-containing matrix "thereafter-to be applied to said surface, the-ste'p'of plowing in said surface a shallow continuoushelicalgroove, with the coursesthereof relatively close together, by means of a'sharpened tool applied with'areverse rake in relation to its direction of travel upon said surface and at such an angle there-to as to 'form a series of minute upwardly-projecting tongues of metal integral with the metal of said :surface along the lip between adjacent courses of said groove.

FOLLIARD 'F. GILMORE. FRANK W. KOTIJER. 

